# -*- coding=utf-8 -*-
# 这个例子是Python版本的单链表

class Node(object):
  def __init__(self, value, next=0):
    self.value = value
    self.next = next # 指针


class LinkedList(object):
  # 链表的数据结构
  def __init__(self):
    self.head = 0 # 头部

  def __getitem__(self, key):
    if self.is_empty():
      print 'Linked list is empty.'
      return
    elif key < 0 or key > self.get_length():
      print 'The given key is wrong.'
      return
    else:
      return self.get_elem(key)

  def __setitem__(self, key, value):
    if self.is_empty():
      print 'Linked list is empty.'
      return
    elif key < 0 or key > self.get_length():
      print 'The given key is wrong.'
      return
    else:
      return self.set_elem(key, value)

  def init_list(self, data): # 按列表给出 data
    self.head = Node(data[0])
    p = self.head # 指针指向头结点
    print p, self.head
    for i in data[1:]:
      p.next = Node(i) # 确定指针指向下一个结点
      p = p.next # 指针滑动向下一个位置
    print self.head.next.next

  def get_length(self):
    length = 0
    p = self.head
    while p != 0: # 0 值就是Node结点中默认的 0 值，表示下一个结点没有了，即没有为其赋值
      length += 1
      p = p.next
    return length

  def is_empty(self):
    if self.head == 0:
      return True
    else:
      return False

  def insert_node(self, index, value):
    if index < 0 or index > self.get_length():
      print 'Can not insert node into the linked list.'
    elif index == 0:
      temp = self.head
      self.head = Node(value, temp)
    else:
      p, post = self.head, self.head
      for i in xrange(index):
        post = p
        p = p.next
      temp = p
      post.next = Node(value, temp)

  def delete_node(self, index):
    if index < 0 or index > self.get_length()-1:
      print "Wrong index number to delete any node."
    elif self.is_empty():
      print "No node can be deleted."
    elif index == 0:
      temp = self.head
      self.head = temp.next
    elif index == self.get_length():
      p = self.head
      for i in xrange(self.get_length()-2):
        p = p.next
      p.next = 0
    else:
      p = self.head
      for i in xrange(index-1):
        p = p.next
      p.next = p.next.next

  def show_linked_list(self): # 打印链表中的所有元素
    if self.is_empty():
      print 'This is an empty linked list.'
    else:
      p, container = self.head, []
      for _ in xrange(self.get_length()-1):
        container.append(p.value)
        p = p.next
      container.append(p.value)
      print container

  def clear_linked_list(self): # 将链表置空
    self.head = 0

  def get_elem(self, index):
    if self.is_empty():
      print "The linked list is empty. Can not get element."
    elif index < 0 or index > self.get_length()-1:
      print "Wrong index number to get any element."
    else:
      p = self.head
      for _ in xrange(index):
        p = p.next
      return p.value

  def set_elem(self, index, value):
    if self.is_empty():
      print "The linked list is empty. Can not set element."
    elif index < 0 or index > self.get_length()-1:
      print "Wrong index number to set element."
    else:
      p = self.head
      for _ in xrange(index):
        p = p.next
      p.value = value

  def get_index(self, value):
    p = self.head
    for i in xrange(self.get_length()):
      if p.value == value:
        return i
      else:
        p = p.next
    return -1


l = LinkedList()
print "The length of linked list now is: ", l.get_length()
print l.is_empty()
l.init_list([1, 5, 12, "fjd", 45, 999])
print "The length of linked list now is: ", l.get_length()
print l.is_empty()
l.insert_node(4, 100)
l.insert_node(6, "cecil")
l.show_linked_list()
print "The value of index 0 is: ", l.get_elem(0)
l.set_elem(0,1000)
l.show_linked_list()
print "the index of *** is: ", l.get_index(1009)
print "The length of linked list now is: ", l.get_length()
l.delete_node(3)
#l.clear_linked_list()
l.show_linked_list()